Sound field variability in the presence of an Internal Kelvin Wave in the Sea of Galilee

Abstract

The spatiotemporal variability of low- and mid-frequency sound field in the presence of an internal Kelvin wave (IKW) is studied theoretically and in an experiment in the Sea of Galilee, Israel. Measurements of the sound field were carried out using a vertical line array (VLA) of ten hydrophones with 3 m spacing, deployed in the lake’s the deepest (37m) part. Signals were transmitted from the source deployed near the shore (depth 8m) at the distance of 5.5km from the VLA. A set of ten 5-second long, linear frequency modulated pulses were transmitted during >24h (the IKW’s period). IKW was registered using three thermistor chains positioned along an offshore transect. This arrangement of thermistor chains made it possible to estimate changes in temperature and sound speed with depth along the entire transect. Variations of the vertical structure of the sound field registered with the VLA can be explained by temporal variability of water layer due to IKWs. The modeling of the sound propagation was done using a Parabolic Equation method, considering the real parameters of the gas-saturated bottom and the bathymetry. Results of modeling are partially verified in the experiment. [This work was supported by Israel Science Foundation, grant 565/15].